While the present invention of an interlocking rivet assembly can be effectively used in a plurality of different riveted configurations, it will be described for clarity as used in a transfer station of an electrostatic marking system such as electrophotography.
By the way of background, in marking systems such as electrophotography or other electrostatographic processes, a uniform electrostatic charge is placed upon a photoreceptor belt or drum surface. The charged surface is then exposed to a light image of an original to selectively dissipate the charge to form a latent electrostatic image of the original. The latent image is developed by depositing finely divided and charged particles of toner upon the belt or drum photoreceptor surface. The toner may be in dry powder form or suspended in a liquid carrier. The charged toner, being electrostatically attached to the latent electrostatic image areas, creates a visible replica of the original. The developed image is then usually transferred from the photoreceptor surface to a final support material such as paper and the toner image is fixed thereto to form a permanent record corresponding to the original.
In these electrostatic marking systems, a photoreceptor belt or drum surface is generally arranged to move in an endless path through the various processing stations of the Xerographic process. Sometimes, as noted, the photoreceptor or photoconductor surface is in the form of an endless belt and in other systems it is in the form of a drum. In this endless path, several Xerographic-related stations are traversed by the photoconductive belt or drum, one of said stations being the transfer station where the toned image is transferred from the photoconductive surface to a final support media such as paper. Many of these marking systems utilize a transfer assist blade assembly (TAB) within the transfer station subsystem to provide unparalleled transfer performance with a wide variety of substrates. Examples of typical TAB assemblies are disclosed in U.S. Pat. Nos. 4,947,214; 5,568,238; and 6,687,480. The disclosures of these patents are incorporated by reference into the present disclosure. The TAB typically is composed of a multitude of parts accurately nested together to form a high precision structure that is used to provide pressure to the backside of a sheet towards the photoreceptor surface. When the blade is actuated against the paper the critical parameter for proper blade force (deletion free prints) and non-toner contaminated backside sheets is blade angle. The blade angle is controlled by the upper extrusion feature and the ability of the clamp to constrain the layers against this feature to maintain a 90 degree angle. The problem is that over time and actuation life (life is approximately 1.5 million cycles) the clamp moves away from the extrusion feature and the blade angle changes (increases). In one embodiment, the clamp is held against the extrusion by eight low profile (space constraint) rivets along its length. Though the rivets are very tight initially, the plastic blade laminate, squeezed between the clamp and the extrusion, creeps/relaxes over time and use, ultimately lowering the force exerted on the clamp. Hence, with reduced force the clamp more easily slips during operation. These rivets are generally made of a relatively soft material such as aluminum, plastic or other comparably soft composition. As these rivets loosen because of extensive continuous use of the transfer blade assembly (TAB), many problems occur that could easily cause imaging and performance problems in the entire marking system. A faulty TAB could scratch or mar the photoconductive surface, tear the paper-receiving sheets and contaminate the blade and future copies with loosened toner particles. Also poor toner transfer from the photoconductive surface to the paper could occur. As noted, a main cause of a faulty TAB is the loosened rivets caused by relaxation of the plastic blade material, cyclic vibration and the counter-reactive force of the TAB against the back of the paper supported by the photoconductive surface. These problems can occur in both color and monochromatic marking systems. Movement of this clamp is the basic problem attended to by the present embodiments.